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Environmental control is an at tempt to produce conditions which are stable in time and spatially uniform. This is not yet possible in standard greenhouses and hence, there is a serious risk that experimental data from plants grown in supposedly con trolled environments may be misinterpreted due to the imperfect know ledge of the parameters under control. Since uncontrolled factors may have important subsidiary effects on plants, measurement is the first step to cope with such situations. Few experiments have been designed specifically to study the climate in a heated greenhouse (1). In particular, little quantitative information exists on variation of inside conditions with time of year, time of day, and the variation of external meteorological conditions. This report deals mainly with the latter, that is, the influence of two types of winter situation, a cool overcast day and a cold clear day, on the climate of a green house. The magnitude and standard deviation of various temperature differences for nighttime and daytime conditions were determined on these two days. This provided information for determining the influence of the time of day on temperature differences under completely different meteorological conditions. A similar temperature comparison was also made from two sets of data on days one month apart with the same number of hours of sunshine. This was done to find out how temperature differences, for the same time of day, are influenced by time of year. Also investigated was the variation in radiation at various locations within the greenhouse considering the time of day and year. Finally, the periods of oscillation of the inside temperature were studied to determine the frequency of observations necessary to account for most of the temporal variations at various locations.
variations of meteorological factors in a greenhouse
Desjardins, R. L. and Geo. W. Robertson 1968. VARIATIONS OF METEOROLOGICAL FACTORS IN A GREENHOUSE. Canadian Agricultural Engineering 10(2):85-90.
85 - 90